The rights plan gives all Siebel shareholders as of Feb. 13, 2003, the option to buy a new series of preferred stock at a discounted rate in the event of a hostile bid. The plan would take effect if a person or group purchased 15 percent or more of Siebel's common stock.
The company said it adopted the plan as a preventive measure against abusive takeover tactics and not in response to any particular proposal.
Such plans, also known as poison pills, make an acquisition more costly and time-consuming for the buyer and are typically adopted when management believes the company vulnerable to a takeover because of a drop in its stock price.
Amid a prolonged downturn in the information technology market, Siebel's stock has steadily declined over the past year. The company's shares closed at $8.87 on Wednesday, down from a 52-week high of $37.21 last spring.
Siebel, the maker of a top-selling set of business-management applications for streamlining corporate sales and customer service, has reported netfor the last two quarters and has seen revenue fall for two years.
Its chief executive, Tom Siebel, recently agreed to26 million stock options the company had granted him, reducing his stake in the company from 13.5 percent to 10.7 percent. The company canceled the options in response to criticism that its generous granting of stock options has diluted the value of its shares.